<HTML><HEAD><TITLE>-(+Number1, +Number2, -Result)</TITLE>
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<H1>-(+Number1, +Number2, -Result)</H1>
Evaluates the difference Number1 - Number2 and unifies the resulting value
with Result.


<DL>
<DT><EM>Number1</EM></DT>
<DD>A number.
</DD>
<DT><EM>Number2</EM></DT>
<DD>A number.
</DD>
<DT><EM>Result</EM></DT>
<DD>A variable or a number.
</DD>
</DL>
<H2>Description</H2>
   This predicate is used by the ECLiPSe compiler to expand evaluable
   arithmetic expressions.  So the call to -(Number1, Number2, Result) is
   equivalent to
<PRE>
    Result is Number1 - Number2
</PRE>
    which should be preferred for portability.
<P>
   The result is of type breal if any of the arguments is a breal,
   else float if any of the arguments is a float, else rational if any
   of the arguments is a rational.  Only when both arguments are
   integers is the result an integer.

<P>
   In coroutining mode, if Number1 or Number2 are uninstantiated, the call
   to -/3 is delayed until these variables are instantiated.

<P>

<H3>Modes and Determinism</H3><UL>
<LI>-(+, +, -) is det
</UL>
<H3>Exceptions</H3>
<DL>
<DT><EM>(4) instantiation fault </EM>
<DD>Number1 or Number2 is not instantiated (non-coroutining mode    only).
<DT><EM>(24) number expected </EM>
<DD>Number1 or Number2 is not of a numeric type.
</DL>
<H2>Examples</H2>
<PRE>
Success:
      -(5, 2, 3).            (gives Result = 3)
      -(5, -2.0, Result).    (gives Result = 7.0)
Fail:
      -(1, 2, 3).
      -(1, 2, 3.0).
      -(5, 2, r).
Error:
      -(A, 2, 6).             (Error 4).
      -(4 + 1, 2, 3).         (Error 24).



</PRE>
<H2>See Also</H2>
<A HREF="../../kernel/arithmetic/is-2.html">is / 2</A>
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